Lecturer: Dr. Ido Ben-Dayan Affiliation: DESY, Theory Group, Universität Hamburg Abstract: Precision Cosmology requires us to take into account the small scale inhomogeneities in the Universe when discussing cosmology. After a general introduction, I will discuss the effect of small scale inhomogeneities on the luminosity distance - redshift relation within LCDM: 1) How inhomogeneities bias the Hubble parameter due to peculiar velocities. This bias ameliorates the tension between CMB and and Supernovae measurements of the Hubble parameter. 2) How inhomogeneities serve as a probe of the primordial power spectrum on small scales through the lensing dispersion of Type Ia Supernovae. Additional details of the upcoming Astrophysics' seminars can be found on the following link. ‏האירוע הזה כולל שיחת וידאו ב-Google Hangouts. הצטרף: https://plus.google.com/hangouts/_/mail.huji.ac.il/astrophysics?hceid=bWFpbC5odWppLmFjLmlsX2c0czhydDlpcmhwZzRvdGNybWIzZGFqcjdvQGdyb3VwLmNhbGVuZGFyLmdvb2dsZS5jb20.75q381cchhhatd1psh6clq2r5s&hs=121